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PMDG 777 Nose Wheel Steering after pushback

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Captain Kevin:

--- Quote from: CapnTibbs on December 28, 2021, 11:13:18 pm ---I don't see how that tells you nothing but that's fine I'll try a different way of explaining it. I normally don't use the tiller axis on the 777
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That's the part I was trying to figure out because up until now, I had no clue if you even used the tiller axis or not because this point wasn't clear and I'm just a truck driver, not a mind reader.

--- Quote from: CapnTibbs on December 28, 2021, 11:13:18 pm ---but I turned it on in the air to see if that would keep the nose wheel tracking straight once I was on the ground. When I dropped the gear, the nose wheel had straightened out so I figured that had sorted the problem but it clearly hadn't. As I said before, on the landing rollout through about 50-60kts just as I was about to vacate the runway the aircraft violently and uncontrollably pivoted to the left.
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You really can't use the tiller at more than 20 knots or the plane just loses it. Something in the PMDG coding somewhere. I don't know what you had set for the tiller or if having nothing set for the tiller could cause it. The rudder can still steer the nose gear, but up to I think 7 degrees, so you'd really only use it for a high-speed exit after landing.

--- Quote from: CapnTibbs on December 28, 2021, 11:13:18 pm ---Obvious question, seeing I did try resetting Couatl if resetting Couatl doesn't fix the problem then it isn't a problem with GSX?
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I got nothing.

virtuali:

--- Quote from: CapnTibbs on December 28, 2021, 09:39:08 pm ---Just to clarify. Here's a photo from after I parked up. The rudder is neutral and there is no pressure being applied on the rudder here. Obviously before the pushback it didn't look like this.
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As I've said, GSX ONLY acts on the rudder and ONLY during pushback so, if the rudder looks neutral at the end of the pushback, it's clear GSX has done what it's supposed to do.

IF the rudder was still deflected at the end of the Pushback, it might have been a GSX issue that, for some reason, failed to release control over it when it's supposed to. But since it seems from all your reports this is not the case, it's very likely the real issue is with the PMDG Nose steering system ( which GSX DOES NOT touch ) being confused by the fact the airplane code wasn't the only thing that controlled the rudder during pushback.

And that's precisely why GSX has a public documented variable to inform airplane developers that GSX is pushing, so they can momentarily turn off any custom simulation of the rudder/steering or anything else ONLY THEM CAN POSSIBLY KNOW that might be affected if something external is pushing.

It's a simulation of what happens in real life with the bypass pin: a mechanical system that decouples the steering from the hydraulic system, allowing the tow truck to be in control.  Our public variable is sort like a "software bypass pin", and other developers like FS Labs, Aerosoft or Leonardo SH, which ALL have their own custom system to simulate steering and hydraulics in general, which they know should be turned off during pushback but only them can possibly know what should be change in their custom code to support that, that's why the proper and safe way to do this is to have GSX telling the plane is pushing, and rely on the plane code doing what it needs to be done to ensure no strange issues like these happens.

When airplane developers use custom code to create non-standard systems not available in the sim (or if they redo systems in a different way), there's no way for us to access those, unless they have specific hooks in an SDK made for that airplane but, while PMDG doe have an SDK for the 777, it mainly provides with events to trigger button/switches in the VC, so it's mostly useful for cockpit builders, sure I can't find anything about temporarily disable the hydraulic simulation or control the steering, which I guess should be required to eventually fix the problem from GSX side.

CapnTibbs:
Okay Umberto thanks for the explanation. I've already sent in a support ticket to PMDG but I haven't heard back from them

CapnTibbs:
After some back and forths with PMDG and some self testing in the sim, I'm pretty sure the issue might well have been as simple as an intermittent USB port triggering at just the wrong moment.

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